Septic Arthritis in Anterior Cruciate Ligament Surgery

Patient Factors

The importance of host physiology in musculoskeletal infections has been emphasized in the literature. Systemic host factors include comorbidities that may compromise the host defense against pathogens. A recent study demonstrated that diabetes mellitus was a significant risk factor for postoperative SA after ACL reconstruction. Patients with diabetes had an infection rate of 8.7% compared with 0.77% in patients without diabetes. A study on persistent infections reported comorbidities in three out of five patients. Sonnery-Cottet et al. reported a significant increase of SA in professional athletes compared with nonprofessional ones (5.7% vs. 0.37%).

Local Factors

Local risk factors for SA after ACL reconstruction include previous or concomitant secondary knee procedures. Potential explanations include the increased operative time, additional or larger incisions with more extensive dissection in cases where complex reconstructive surgery takes place, and implantation of additional foreign material. A large registry study reported that deep surgical site infection developed in 0.8% (9) of 1091 revisions, compared with 0.3% (44) of 15,101 primary ACL reconstructions.

Graft Type

Graft choice has been implicated as a risk factor for SA after ACL reconstruction. Despite concerns that allograft tissue may result in a higher infection risk compared with autograft, this has not been demonstrated in the literature. In contrast, hamstring autograft has been the graft type associated with a higher risk for infection.

Maletis et al. demonstrated a significant association of graft type with infection in a large registry. Deep surgical site infection developed in 0.61% (20) of 3257 patients who received hamstring autograft compared with 0.27% (12) of 4404 patients with allograft and 0.07% (2) of 2965 patients with bone–patellar tendon–bone (BPTB) autograft. The likelihood of a patient with a hamstring autograft having a deep infection was significantly higher than that of a patient with a BPTB autograft (odds ratio 8.2, P = .01). The likelihood of a patient with an allograft having a deep infection was higher—but not significantly—compared with a patient with BPTB autograft (odds ratio 3.6, P = .10).

Brophy et al. reported a SA rate of 0.3% (3 of 931) in patients receiving BPTB autograft, 1.3% (8 of 639) in patients receiving hamstring autograft, and 1% (6 of 628) in patients who received allograft. The risk was significantly increased with use of hamstring autograft compared with BPTB autograft (odds ratio 4.6, P = .026) and with use of allograft compared with BPTB autograft (odds ratio 4.3, P = .047).

The increased infection risk associated with hamstring autografts may be attributed to the additional surgical dissection and the potential for formation of hematoma. Inadequate sterilization of equipment, such as tendon harvesters, may play a role.

Contamination of Instruments

Contaminated inflow cannulas have been identified as a source of infection. Viola et al. reported a sudden increase in their infection rate from 0.1% (period from 1991 to 1996) to 14.2% (period from December 1996 to February 1996). “Sterile” sets of inflow cannulas used for ACL reconstructions were found to be contaminated with coagulase-negative Staphylococcus. Following the discovery of the contaminated instruments, the infection rate dropped to 0.25%.

In another study, contamination with coagulase-negative Staphylococcus was present on supposedly sterile suture clamps on graft preparation boards. Inadequate disinfection of arthroscopic equipment and flash sterilization of meniscus repair cannulas with residual debris in the lumen have been reported as potential causes of SA following arthroscopy. Failure to disassemble a tube-within-a-tube tendon harvester during the sterilization process has also been implicated in postoperative infections after ACL reconstruction.

A study that investigated clusters of infections after ACL reconstruction found shortfalls in the decontamination and sterilization of surgical equipment, as well as wide variation in perioperative care practices among surgeons. Implementation of ACL pathway guidelines significantly reduced the infection rate from 1.96% (24 of 1226 cases from 2002 to 2008) to 0% (0 of 500 cases from 2008 to 2011).